Re: strict copy_from_user checks issues?

[H. Peter Anvin]

On 01/07/2010 06:02 AM, Arnd Bergmann wrote:
> On Tuesday 05 January 2010, H. Peter Anvin wrote:
>> What's much worse is that it adds churn to an otherwise-tested code path.
>>
>> We almost need a copy_from/to_user_audited() to override the warning.
>> Not that errors can't creap back in...
>>
> 
> Maybe just splitting it up into access_ok() and __copy_from_user(),
> plus a comment is enough? That way we don't need to add another interface
> for the rare case.
> 

Adding a named interface makes it clear *what* you are doing and
*why*... just open-coding the implementation does neither.

> On a related topic, one interface that may actually be worth adding is
> a get_user/put_user variant that can operate on full data structures
> and return -EFAULT on failure rather than the number of remaining
> bytes that 99% of the code never need.

What is wrong with checking for zero?

	-hpa

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